What was the code name for the planned Allied invasion of the Japanese home islands in 1945?

Operation Downfall was the code name for the planned Allied invasion of the Japanese home islands.

The plan consisted of two major stages. Operation Olympic was scheduled to land on Kyushu in November 1945, while Operation Coronet was planned for the Honshu plain near Tokyo in March 1946. Downfall was the umbrella name for both operations rather than the name of only one landing.

The invasion was never carried out because Japan announced its surrender in August and signed the surrender instrument in September. Allied planners nevertheless prepared extensive forces, shipping, air support, and casualty estimates for a campaign expected to be extremely difficult. Japan was also organizing civilian and military resistance for a possible landing.

Operation Downfall is often confused with Olympic or Coronet. Olympic referred to the southern Kyushu operation; Coronet referred to the later Honshu operation. Another separate plan, Operation Starvation, was the U.S. naval mining campaign against Japanese ports and waterways. The cancellation of Downfall left its projected human cost a matter of historical debate rather than an actual battle total.